Public Utilities Board Drainage Department STANDARD SPECIFICATION FOR DRAINAGE WORK
PUBLIC UTILITIES BOARD
INDEX TO STANDARD SEPCIFICATION FOR DRAINAGE WORK
PART I - GENERAL
2Measurement Of Settlement……………1
3Working With Other Contractors……………1
6Flow Of Traffic
10Site Surveying Work
13Office For S.O.
15Continuous Working And Overtime…………6
16Flow Through Drain And Canal……………6
17Pollution Control Measures And Prevention Of Mosquito Breeding6
18Rate Of Excavation And Drain Construction………7
19Safeguarding Properties Adjacent To Site
20Method Of Working
21Cofferdam And Temporary Tidegates…………8
22Preservation Of Trees, Vegetations And Top Soil
24Protection Of Work
25Demolition And Making Good……………9
27Prevention Of Flotation
28Inspection And Replacement Of Defective Work………10
29Reinstatement Of Surface
30Reinstatement Of Foundation And Road Surface………11
31Nominated Sub-Contractor And Other Supplier………12
PART II - MATERIAL
32Standard Of Material
33Sample Of Material
42Testing Of Steel
45Expansion Jointing Material……………17
46Joint Sealing Compound
48Requirements On Precast Concrete Units…………18
49Prestressed Concrete Slab
50Concrete Pipe (Ordinary Portland Cement) Without Lining…20
54Stone For Pitching
57Grating & Chequer Plates For Closed Drain/Culvert……22
61Erosion Control Blankets
PART III - WORKMANSHIP
66Excavation In Rock
68Preventing Damage Due Subsidence…………29
69Timbering Of Excavation
71Steel Trench Sheeting
72Steel Sheet Piling
73 Liability For Timbering
76Approval Of Excavation
78Withdrawal Of Timbering
79Disposal Of Surplus Excavated Materials And Unwanted Materials33
80Filling And Embankment Work……………34
84Storage Of Cement
85Testing Of Cement
86Sample Of Aggregate
87Storage Of Aggregates
88Batching Of Concrete
91Site Testing Of Aggregate
……………3992Workability & Consistency Of Concrete…………39
93Testing Of Concrete Cube
95Premix And Ready-Mixed Concrete…………43
97Handling And Transporting Concrete…………44
99Compaction Of Concrete
100Concreting Through Water……………47
101Finish Of Concrete
102Protection And Curing Of Concrete…………48
103Tests On Hardened Concrete……………49
111Fixing Fabric Reinforcement……………53
114Removal Of Formwork
115Boxing Or Cutting Out
116Building And Grouting In
117 Bonding Ties
BRICKWORK, PLASTER AND TILING
127Mortice, Hole, Chase, Etc
128Damp Proof Course
129Preparation Of Surface For Rendering And Screeding……60
130Cement Mortar Rendering
131Waterproof Cement Mortar Rendering…………60
133Floor Tiling Screed
PIPE CONDUIT DRAIN
135Pipe Bedding With Granular Material…………62
136 Concrete Bed, Haunching And Surround To Pipe………62
139Jointing Concrete Pipe
141Fracture Of Pipe
143Painting Metal Surfaces
144Painting Cement And Sand Plaster Surfaces………70
146Excavation To Formation
147 Preparation Of Sub-Grade
149Sub-Base And Base
……………79150Asphaltic Wearing Course
157Maintenance Period Inspection……………91
REQUIREMENT FOR PERMANENT REINSTATEMENT
Page3Advice Of Commencement Of Work…………92
5Lighting, Watching & Protection……………92
6Supply Of Granite
8Material For Hotmix Asphalt……………93
9Asphalt Mixing And Delivery……………94
10Extend Of Permanent Reinstatement…………95
11Complete Reinstatement In Roads……………95
12Partial Reinstatement In Road……………95
13Maintenance Of Trenches Prior To Permanent Reinstatement…96
14Excavation & Backfilling
15Removal Of All Excavated Material…………96
16Roller And Rolling
19Hotmix Asphalt Surfacing
20Top Soiling And Turfing
21Reinstatement Of Drains & Precast Unit…………98
22Concrete For Reinstatement Work……………99
23Reinstatement Of Other Surface……………99
24Inspection Of Completion Work……………99
25Maintenance Of Surface
PART I - GENERAL
(a)The Contractor shall note that the description of the Works embraced in the Contract, as given in the Contract Specification, is a guide and he shall make all necessary checks and investigations to ascertain the actual nature and scope of work.
(b)It must be clearly and definitely understood by the Contractor that he will be deemed to have visited the whole of the site and ascertained the nature of the area, accessibility to the work site, location of the site accommodation, etc. The Contractor will be held solely responsible for making all the detailed arrangements and co-ordinating with the owners of all lands when he executes any part of the works that enter or affect such land.
(c)The Contractor is advised that it will be deemed to be his sole responsibility to ascertain for himself the extent of work that is required to be done on site and to generally obtain his own information on all matters affecting the complete execution of the Works to the entire satisfaction of the S.O. as no claim for extras, in consequence of any alleged ignorance in any respect, will be entertained by the Board.
(d)Although various buildings, sewers, drains, etc may be shown on the drawings, the Contractor will be held solely responsible for making his own investigations and for allowing for any extra costs in his rates due to the presence of all obstructions, whether indicated on the drawings or not.
2MEASUREMENT OF SETTLEMENT
Measurement of settlement shall conform to S.S. CP4. For each test, two signed copies of the field readings and the graphs shall be submitted to the S.O. within 3 working days on completion of the test.
3WORKING WITH OTHER CONTRACTORS
The Contractor is advised that there may be other Contractors working within the site area. The Contractor may therefore be given joint possession in some sections of sites with the other Contractors for the purpose of carrying out his contractual obligation and he shall in no way interfere with, impede or otherwise prevent these other Contractors from carrying out their contractual obligations. The Contractor shall allow in his prices, when tendering, for affording reasonable facilities to the other Contractors and for any interference with his work from these other contract operations.
The Contractor shall take all due care and necessary precautionary measures to ensure that no damage occurs to any existing sewer, water or gas mains, electricity or telephone cables, culvert and any other existing services. Any damage arising out of the Contractor’s work in such respect will be made good to the entire satisfaction of the S.O. by the Contractor at his own expense and no claim to the contrary will be entertained by the Board.
(a)The Contractor will be held solely responsible for maintaining clean, safe, adequate and free pedestrian and vehicular access to the various premises adjacent to the Works. The Contractor shall maintain clean, safe, adequate and free passageway along routes within the working space.
(b)The Contractor will also be required to provide facilities to the working site or sites. Such access must be properly constructed and maintained to afford a safe access to pedestrians and vehicles. The access may be made available to any other Contractors and supervisory staff on the instructions of the S.O..
6FLOW OF TRAFFIC
(a)The Contractor shall ensure that the flow of traffic on the roads and access is maintained at all times during the contract. The Contractor is to provide such flagmen, approved signs and signalling equipment as may be necessary day and night to control the traffic to the satisfaction of the S.O. and the appropriate Controlling Authority. In the planning and execution of any temporary or permanent works which may affect the traffic flow and/or access to site or other properties, the Contractor shall co-operate closely with the S.O. and the appropriate Controlling Authority.
(b)Whenever required by the S.O., the Contractor shall remove with due compliance and at his own expense any plant, machinery, staging and other materials which may interfere with traffic and the use of roads, footpaths or open spaces on the site or adjacent thereto.
Such information as is known to this Department will be made available to the Contractor. The Board does not, however, extend any guarantee as to the accuracy of such information.
Should there be any discrepancies among the Drawings, Specifications and Bills of Quantities, the Contractor shall refer the matter to the S.O. before commencement of work. The S.O. will decide as to which document will take precedence and his decision will be final. No claims to the contrary shall be entertained by the Board.
(a)The Contractor is required to confine his working areas within the worksite and not to encroach onto adjacent properties. The Contractor is to note that he is required to procure for himself at his own costs any additional working and storage spaces.
(b)The Contractor shall ensure that the movement of his vehicles in and out of the site shall not hamper the free flow of vehicular and pedestrian traffic.
(c)The Contractor shall take every precaution to prevent his employees from trespassing on lands outside the contract site.
(d)The Contractor shall ensure that the area and access under use is properly maintained and that they would be reinstated to their original state upon completion of the work all to the entire satisfaction of the S.O..
10SITE SURVEYING WORK
(a)The Contractor shall provide a full-time officer competent in surveying on site to carry out engineering survey.
(b)The Contractor shall provide and maintain in good working condition on site at all times a levelling instrument and theodolite and such other equipment and personnel as the S.O. may require for the checking and measuring of works.
10.2SETTING OUT AND LEVELS
(a)The Contractor shall engage a Registered Surveyor and supply all labour, material and equipment necessary for the setting out of the works in accordance with the Contract and Drawing Specifications, or as required by the S.O.. The setting out shall be carried out by a Registered Surveyor and certified by him.
(b)The lines to be set out on site shall generally include a base line, the proposed drain lines, drainage reserve lines, limits of the working space where specified in the Contract and any other lines as required by the S.O., including any amendments. These lines shall be marked clearly on site by planting pegs or posts with paint markings on the ground, or any other means as approved by the S.O..
(c)The Contractor shall submit a ‘setting out’ plan duly endorsed by Registered Surveyor, to the S.O. for his written approval, prior to the commencement of work. The ‘setting out’ plan shall be in the same scale as the Contract site plans, and shall show the alignment of the base lines, proposed drain lines, Drainage Reserve lines and any other lines as set out on site. The plan shall also show other permanent structures and features in the vicinity of the works such as buildings roads, side drains, culverts bridges, fencing, services pipes or cables crossings.
(d)The Contractor shall carry out the works strictly in accordance with the approved setting out plans. Any deviation from the plans shall be forwarded to the S.O. for his acceptance and, if accepted by him, shall be recorded on an amended setting out plan.
(e)Any assistance which the S.O. may render to the Contractor in setting out shall in no way relieve the Contractor of the entire responsibility for the correctness of all setting out.
The Contractor shall establish adequate numbers of bench marks and fixed points on the site to the S.O.’s direction and shall ensure that these are not damaged and disturbed. All such bench marks and fixed points shall be based on a Government Bench Mark.
The Contractor shall make his own arrangements and pay, where necessary, for the supply of electricity required for the constructional purposes.
13OFFICE FOR S.O.
(a)The Contractor shall provide on an approved site, a weather and sun proof lock-up office with mortice lock or approved strong hasp, staple and padlock to the door. The size and type of office shall be designed and built to the satisfaction of the S.O.. It shall include proper modern sanitary facilities, washing facilities, electricity, electrical appliances, telephones, furniture and fitments etc., all to the approval of the S.O. and for the exclusive use of the S.O. and his staff.
(b)The following adequate furniture and equipment shall be provided and maintained in good and usable conditions in the site office:-
(i)1 no. 1500mm x 900mm writing table with 2 locked drawers
(ii)1 no. arm chair, circular
(iii)2 nos chairs, straight-back
(iv)1 no. 1500mm x 900mm drawing table with 2 plan drawers and 1 stool
(v)1 no. telephone
(vi)1 no. first aid kit
(vii)1 no. fire extinguisher
Other necessary office and drawing equipment such as drawing board, T-square, set-squares, scales, pencils, etc.
(c)The office shall be located on an approved site in close proximity to the work and the Contractor shall move the offices as often as the S.O. may direct to keep pace with the work. The Contractor is deemed to have allowed for this in his pricing.
(d)Allow for maintaining all the offices and facilities for the duration of the contract including paying all charges and keeping in a clean condition.
(e)The Contractor shall arrange for the office to be provided with telephone facilities and shall keep the telephone connected as long as it is required and shall pay all charges for installation, rent and telephone calls made by the S.O. and his staff.
(f)The Contractor shall also provide covered car parking facilities adjacent to the office to the approval of the S.O..
(g)On completion of the Works and only instructed by the S.O., the contractor shall remove the office together with all its facilities from the site and leave the site in a tidy condition.
(a)All mechanical plants used by the Contractor in the execution of the Works must be of such type, size and of such method of working as the S.O. shall approve.
(b)The S.O.’s approval to the use of mechanical plants will not be unreasonably withheld, but if in the S.O.’s opinion, circumstances arise which make it desirable that the use of plants should be suspended either temporarily or permanently, the Contractor shall change the method of performing the work affected at his own cost. The Contractor will be deemed to have no cause for claim against the Board on account of having to carry out the work by another method nor will he be deemed to have cause for claim if any other instructions issued by the S.O. results in the mechanical plant having either to stand idle for a period of any duration whatsoever or to be removed.
(c)This clause shall apply also to the plants which, in the opinion of the S.O., are not as quiet in operating as the circumstances seem to the S.O. to warrant.
(d)The Contractor shall use every possible means to prevent noise and annoyance to the residents of the neighbourhood in which the Works and the Contractor’s storage yards are situated and all the machinery must be of such design and so arranged to be reasonably free of noise in working.
(e)All equipment and plant being used on the Works shall be equipped with noise control devices complying with all laws and regulations prevailing at the time of use.
(f)The Contractor will not be allowed to make any extra charge for work or expense incurred in complying with the requirements of this clause.
15CONTINUOUS WORKING AND OVERTIME
(a)If, in the opinion of the S.O., it is necessary, by reason of the safety of the works, or for the restoration of interrupted services or for any other reason whatsoever, the Contractor shall, when so ordered carry out the works or any portion thereof continuously by day and by night without extra charge.
(b)The Contractor, if he considers that it may become necessary to cause overtime to be worked on site in order to complete the contract by the date for completion, shall request for written permission and allow for such contingency in his tender price.
(c)It shall be clearly and definitely understood by the Contractor that no claims in respect of any of the above shall be allowed in the settlement of the Final Account.
16FLOW THROUGH DRAIN AND CANAL
(a)The Contractor shall take every practical precaution to avoid interference with the flow of storm water through the drain, canal, culverts and other side drains etc. Any spoil, rubble, timber, rubbish or other materials which may fall or be brought into the drain, canal culvert and other site drains etc by the storm water shall be removed forthwith by the Contractor.
(b)If the S.O. considers that any temporary structure erected in a drain is obstructing the flow to an extent more than necessary making it liable to cause flooding in the event of a rain storm, he may, one hour after notifying the Contractor or his representative, employ whatever labour and plants to demolish such structures at the expenses of the Contractor. Any expenses so incurred will be deducted from any sum that may be due to the Contractor.
(c)All necessary water tight flumes, cofferdams, chutes and/or other approved methods of controlling the flow of water shall be adequate for this purpose in the opinion of the S.O., and shall be constructed in a rigid, workmanlike manner, sufficient to withstand water pressure at its highest level.
(d)The Contractor shall be responsible and shall indemnify the S.O. against any actions, claims, costs and demands for damages caused by flooding, slips, subsidences or other failures resulting from non-compliance by the Contractor with respect to the above.
17POLLUTION CONTROL MEASURES AND PREVENTION OF MOSQUITO BREEDING
The site and working areas shall be maintained at the Contractor’s expense in accordance with the current regulations governing pollution control measures and prevention of mosquito breeding.
18RATE OF EXCAVATION AND DRAIN CONSTRUCTION
The Contractor shall endeavour to so arrange his work that the rate of drain construction keeps pace with the rate of excavation. However, the distance over which the Contractor may excavate in advance of the concreting and drain construction will be specified from time to time by the S.O..
19SAFEGUARDING PROPERTIES ADJACENT TO SITE
(a)Where work is undertaken near or adjacent to buildings and in the opinion of the S.O., the stability of such buildings is liable to be affected as a result of the work, the S.O shall instruct the Contractor to have such buildings inspected and engage an independent condition surveyor, approved by the S.O., to carry out a precondition survey of such buildings. The precondition survey is to record photographic evidence including description of all existing cracks, defects, etc prior to the commencement of the works. A precondition survey report with two complete sets of photographs shall be submitted to the S.O. within 1 month from the date of the site possession and prior to the commencement of the works. Every attempt shall be made to survey all premises. Every precaution should be taken by the Contractor to survey and safeguard all building or structure that are likely to be affected by the construction work and they should be to the complete satisfaction of the S.O.. The Contractor may be directed by the S.O. to excavate in such lengths of excavation as will permit the least amount to be opened at one time in order to minimize the danger of such open excavation affecting the stability of buildings or their supports. The item on precondition survey in the bills of quantities would not be paid unless the S.O. instructs the contractor to carry out the precondition survey.
(b)The Contractor will be held responsible for damage to public, private or other buildings and properties adjacent to the site of the works which is caused as a direct or indirect result of the Contractor’s work. Should the Contractor fail to take the necessary precautions, the S.O. may, after giving the Contractor twenty-four (24) hours notice in writing, instruct another party to supply labour, material, plant, implements and transport to carry out such work. The cost of such work will be charged to the Contractor.
(c)The Contractor must take due care to safeguard all existing services, such as water, sewer or gas mains, electricity or telephone cables, culverts and any other existing services. The Contractor will be required to excavate trial pits in advance of the Works and determine accurately the position of mains, pipes, etc. The Contractor shall notify the S.O. of any mains, pipes or conduits met within trial pits or excavation and shall take steps to support and protect these to the satisfaction of the S.O.. The Contractor will be responsible for any damage done to mains, cables, culverts and other services, inside or outside the excavation as a result of earth movement, faulty timbering, excessive weight of excavated material being deposited too close to open trench, leaving the excavation open for an unduly long period or to any form of settlement following backfilling.
(d)No work done by the S.O. or his workmen nor the fact that the timbering has complied with this Specification or requirements of the S.O. nor the approval of proposed or completed timbering etc by the S.O. shall absolve the Contractor from his responsibilities and he will be required to make good any damage caused as a result of the timbering failing to give proper support to the sides of the excavation.
(e)Furthermore, the Contractor is required to conform with any other safety and fire regulations that may be introduced from time to time.
20METHOD OF WORKING
The Contractor is required to carry out the Works in the manner detailed herein, shown on the drawings and normally adopted. He is at liberty to supply with his tender such modification as he proposes for consideration and shall seek for approval from the S.O. before he is allowed to apply new or changed methods of construction. Notwithstanding any Specification, approval of decision given by the S.O. as to the carrying out of the Works, the Contractor will be wholly liable for the safety of the Works, both temporary and permanent and for the completion of the Contract to the satisfaction of the S.O..
21COFFERDAM AND TEMPORARY TIDEGATES
(a)Any proposal for cofferdams or temporary tidegates shall not be implemented without the prior written approval of the S.O..
(b)Any cofferdams proposed within the existing drain shall be designed such that they are easily removable or collapsible to ensure that the cofferdams are not liable to cause flooding during a rainstorm.
(c)The Contractor shall also provide diversion drains with equivalent conveyance capacities to compensate for the loss of flow capacity due to the obstruction of flow by the cofferdams.
(d)The Contractor shall submit details, such as the method of construction, materials used, width, height, length and location of the proposed cofferdams, temporary tidegates and diversion drains to the S.O. for his approval before commencing work on the proposed cofferdams, temporary tidegates and diversion drains.
(e)If a temporary tidegate is used, the Contractor must submit the operation procedure to the S.O. and the tidegate must have the following features:-
(i) water level sensors to provide an early warning signal when the water in the drain reaches a critical level, which shall be pre-determined by the S.O.;
(ii) an automated paging system with five pre-programmed numbers; and
(iii) 24 hours manning by staff employed by the contractor.
(f)Testing of the water level sensors, auto-paging system and tidegate is required to be carried out at every three months during the entire construction period.
22PRESERVATION OF TREES, VEGETATIONS AND TOP SOIL
All existing trees, vegetation and top soil encountered on site are not to be damaged or removed unless on the expressed instruction of the S.O.. Where existing trees, vegetation or topsoil is to be maintained, the Contractor shall take all necessary precautions to maintain or reinstate all to the satisfaction of the S.O. till the end of the maintenance period.
(a)For concrete and reinforced concrete structures, a fully detailed and explained programme of concreting must be submitted and approved by the S.O. before work may proceed.
(b)The programme shall indicate and/or take cognisance of the method of timbering, levels of struts and frames, arrangement of reinforcement, construction joints and the proposed plant and methods of concreting to be used.
24PROTECTION OF WORK
The Contractor shall, at his own expense, protect all work liable to damage either by the weather or by the method adopted for the execution of the works requiring the use of cement. The Contractor’s attention is drawn to the risk of damage to structures due to temperature changes and he will be required to protect all materials subject to damage from direct rays of the sun.
25DEMOLITION AND MAKING GOOD
(a)The Contractor shall take care when demolishing or cutting away existing work that no adjacent work is unnecessarily damaged in any way. Any work so damaged shall be made good entirely at the expense of the Contractor.
(b)Old materials shall not be re-used in the new work, except where so specified or as directed by the S.O..
(c)Exposed raw faces of existing concrete or brickwork which will not have new work built on them shall be made good with cement, rendering or new brickwork and finished to a neat, straight, vertical or plane surface in harmony with the adjoining surface.
(a)The S.O. may instruct the Contractor to make a loading test on the Works or any part thereof if in the S.O.’s opinion such a test is necessary.
(b)If the test so instructed is to be made because of cube test failure, or the finished work in the opinion of the S.O. is structurally defective and therefore unacceptable unless proven otherwise, then the test shall be made at the Contractor’s expense irrespective of the test result.
(c)For all structural works, the load tests shall be done generally in accordance with B.S.8110.
(d)If the result of any of the tests is not satisfactory, at the S.O.’s instruction, that part of the Works shall be rejected and reconstructed to comply with this Specification, or other approved measures be taken to make the works secure, all at the Contractor’s expense. No extension of time shall be entertained in this connection.
27PREVENTION OF FLOTATION
(a)The Contractor is warned that the structures may not be heavy enough to resist the possible uplift due to water pressure until the structure, soil cover and backfilling have been completed. The Contractor shall make adequate arrangements to keep the excavation dry until the structures and filling are complete or shall adopt other approved means of ensuring the stability of the temporary or permanent works. His proposed method must be submitted to the S.O. for approval before work is commenced and he shall provide for adequate standby plant and attendance throughout 24 hours each day.
(b)For pipelines laid in wet, waterlogged or ground subject to flooding, all necessary precautions must be taken to prevent the flotation or movement of pipelines whether laying, laid or under test.
28INSPECTION AND REPLACEMENT OF DEFECTIVE WORK
(a)At any time during or after the execution of the Works, the Contractor shall, at the request of the S.O. and within such time as the S.O. shall name, open for inspection any work covered up and should the Contractor refuse or neglect to comply with such request, the S.O. shall employ other workmen to open up the same.
(b)If the said work has been covered up in contravention of the S.O.’s instructions, or if on being opened up it be found not in accordance with the Drawings, Specifications and Bills of Quantities or the instructions of the S.O., the expenses of such opening and covering it up again, whether done by the Contractor or such other workmen, will be borne by and is recoverable from the Contractor.
(c)If the work has not been covered up in contravention of such instructions or is found to be in accordance with the said Drawings, Specifications and Bills of Quantities or instructions, then the expenses aforesaid will be borne by the Board and be added to the Contract Sum.
(d)Whenever in the opinion of the S.O. the work done is inadequate or of poor workmanship or inferior materials or in anyway sub-standard, such works will be demolished, cut out or removed from the Works immediately and replaced with new materials of the required standard and quality.
29REINSTATEMENT OF SURFACE
(a)The Contractor's work shall include the reinstatement of the foundation and surfaces of any roads, kerbs, cycle tracks footways and grass areas disturbed by the excavation work both within and outside the actual trench area. The Contractor will be paid for the reinstatement of trenches at the rates given in the Bill of Quantities but no payment will be made for any surfaces disturbed outside the excavation, the reinstatement of all such surfaces being entirely the responsibility of the Contractor.
(b)The Contractor shall allow for machine paving in all reinstatement of road surfaces. If damage caused by the Contractor’s work is extensive, he shall note that reinstatement in the form of milling and patching of premix on road surfaces may be necessary to satisfy LTA on their requirement of the road reinstatement works.
(c)The Contractor shall also allow for the complete reinstatement of all surfaces damaged in side-tables, and all other private or Government Lands to the approval of the S.O. and generally to a condition at least equal to the original ground surface before the Works commence. The Contractor shall note that for tiled surfaces, matching tiles need to be provided by him for the reinstatement works. Where exact matching tiles are unavailable, the Contractor shall note that he may be required to retile areas beyond his immediate work site to the full satisfaction of the S.O. and the other relevant authorities.
30REINSTATEMENT OF FOUNDATION AND ROAD SURFACE
(a)The Contractor will be required to maintain in a clean, safe and tidy state the temporary reinstatement of trench and other damaged surfaces in roads as specified previously until such time as the permanent reinstatement is carried out.
(b)Permanent reinstatement must only be carried out on receipt of an instruction from the S.O. and the reinstatement will then commence within 7 days and completed as soon as possible. The S.O. may instruct the Contractor to reinstate the roads in sections as the work proceeds.
(c)The reinstatement must comply with all the requirements of the Traffic and Road Management, LTA. Any work not conforming in standard or extent to the requirements of the S.O. or Senior Manager of Traffic and Road Management, LTA must be immediately removed and replaced or extended.
(d)Should the Contractor fail to carry out all the required reinstatement works within a reasonable time of him being instructed to do so, the S.O. may arrange for the proper execution of the work at the expense of the Contractor.
(e)On completion of the reinstatement, the Contractor will be required to maintain all the road surfaces etc. affected for the full period of the Contract and Defects Liability Period. All faults, settlements etc. developing within this period must be made good immediately upon receipt of an instruction from the S.O..
31NOMINATED SUB-CONTRACTOR AND OTHER SUPPLIER
(a)Where certain works of supply and erection or fixing are concerned, Nominated Sub-Contractors may be employed. In this event a Prime Cost Sum will form part of the Contract and the Contractor will be instructed to place orders or enter into Sub-Contracts with the Nominated Sub-Contractor.
(b)The Contractor shall give Sub-Contractors and others working on the Site all information reasonably necessary to enable them to set out properly and execute their work. The Contractor shall provide to Nominated Sub-Contractors all relevant copies of Specifications and Conditions of Contract to enable them to comply with all the requirements under the main Contract so far as it relate to sub-contract works.
(c)The Contractor shall provide general attendance upon all Sub-Contractors, Specialists and other executing related work. The Contractor shall provide such facilities as the S.O. may consider reasonable and afford them use of erected scaffolding which they may require for the purpose of carrying out their work, supply them with labour and tackle for unloading, getting in, hoisting and distributing their materials, allow them use of storage for their materials, allow them use of storage for their materials and space for working so that their works may proceed regularly with the general progress of the Works.
PART II - MATERIAL
32STANDARD OF MATERIAL
(a)As far as is practicable and unless otherwise stated, all materials used in the Works shall comply with the current Singapore Standard Specification or equivalent quality standards. Whenever reference is made to National Standards and Trade Names, other approved standards which ensure an equal or higher quality of product or workmanship than the specified will also be accepted.
(b)Wherever any material required for the Works is manufactured in the Republic of Singapore, the Board will give preference to the use of that material in lieu of an equivalent imported material provided that, in the opinion of the S.O., the material is considered satisfactory with regard to quality, etc., and the price is equal or lower than the equivalent imported materials. In any case of doubt, the Contractor should consult the Drainage Department.
(c)Where an approved Standard is quoted in this document, the latest standard will apply.
(d)In all cases where materials are specified to comply with Singapore Standards, the Contractor shall, if required, obtain from the manufacturer and supply to the S.O.'s representative, the appropriate certificates of compliance with the Standards. Notwithstanding the above, test shall be carried out as and when directed by the S.O. in accordance with the relevant Standards.
(e)Where materials are specified to Singapore Standard Specification or equivalent quality standards and the appropriate certificates of compliance are not available, the Contractor shall arrange for the testing of samples. Full tests will be carried out in accordance with the Specification to demonstrate complete compliance. Tests may be carried out by the accredited laboratory on behalf of the Contractor but the cost of samples, transport testing and every other expense shall be borne by the Contractor.
33SAMPLE OF MATERIAL
(a)Samples of aggregates, bricks, tiles and all materials required by the S.O. must be submitted for approval on site before any bulk orders are placed.
(b)Following approval of samples, bulk deliveries may take place and these must at all times be equal or superior in quality than the approved samples. Any materials delivered during the progress of the Works and found to be inferior to the approved samples or unsatisfactory in any other respect must be immediately and completely removed from the site or sites. The Contractor may also be required to produce proof of the destination of condemned materials removed from the sites.
(a)All timber used for timbering of excavation or shoring must be of adequate section and quality. Timber used in trenches to support the face of the excavations must be at least Medium Hardwood as in accordance with the Malaysian Grading Rules for Malaysian Timbers.
(b)The timber used in shuttering must be of sound, well-seasoned timber and free from shakes, twists or other defects. Plywood lining for shuttering must be of an approved thickness and type of timber, resin bonded and water repellent.
(c)Timber used in carpentry and joinery must be sound, thoroughly seasoned and free from defects. The timber shall have a straight uniform grain and be of an approved species for each purpose.
All timber hardboard, etc. to be permanently incorporated into the Works must be pressure impregnated with an approved preservative. The preservative must be of a type resistant to all forms of rot, termite and insect attack.
(a)Bakau piles shall be good, sound, straight piles with fresh uninjured bark and of reasonably uniform size throughout. They shall not be less than 75mm in diameter at the larger end and 65mm at its thinner end. Such measurements shall not be over knobs and protuberances. The permissible deviation of the axis of the pile from the straight line joining the centres of the two ends shall not be more than 15mm.
(b)All bakau piles shall be inspected and approved by the S.O. before being used. Bakau piles that have been rejected shall be removed from site immediately. The piling shall be carried out by operators thoroughly experienced in their trade and shall be carried out in accordance with the instructions of the S.O..
(c)Piles shall be driven vertically in a straight line, particularly squared from the face of the work and free from damage. The monkey used shall be 200 kg (minimum) in weight. The monkey shall drop from a height of 1m minimum but not exceeding 1.5m. The actual height of the drops shall be as directed by the S.O..
(d)Incorrectly or badly driven piles and piles damaged during driving shall be extracted and replaced or else duplicated all at the Contractor’s own expense.
(e)For bakau piles longer that 5m but not exceeding 10m length, only one mild steel splice joint shall be allowed to extend the piles to the required length. No splicing shall be allowed for bakau piles not exceeding 5m in length. Splicing shall be by means of a mild steel collar of 110mm internal diameter and 400mm in length. The collar shall be fabricated from a single galvanised Steel Sheet of SWG 12 (2.64mm) thickness with 15mm diameter mild steel bar strut at the centre of the collar and all shall be well coated with bituminous paint and approved by S.O. before being put to use.
Cement must be ordinary Portland cement of approved manufacture and shall comply with S.S.26 - Specification for Portland Cement (ordinary and rapid-hardening). It must be of an approved brand with preference being given for cement of local manufacture. Where high alumina cement is specified, it shall comply with B.S. 915. Compression tests instead of tensile tests shall be made on cement-sand cubes in order to determine the strength of cement.
(i) Materials used as aggregates must be obtained from a source known to produce aggregates satisfactory for concrete and must be chemically inert, strong, hard, durable, of limited porosity, and free from adhering coats of clay lumps, coal, coal residues, organic or other impurities that may impair the strength or durability of the concrete. Aggregates must be tested in accordance with the requirements of S.S.31 and the results of such tests must be as hereinafter specified, the percentage being by weight unless the context indicates otherwise.
(ii) In the design of concrete mixes, the grading of the combined aggregates shall lay within one of the Zones A, B or C of Road Note 4 issued by the Road Research Laboratory, Department of Scientific & Industrial Research, U.K..
(iii) The S.O. may order the grading of the aggregates to be varied from that specified above and the Contractor will not be entitled to any extra payment for such variation.
(i) Fine aggregate must be clean, natural sand or sand derived by crushing gravel or stone and must be free from coagulated lumps. Sand derived from stone unsuitable for coarse aggregate must not be used as fine aggregate.
(ii) The sodium hydroxide test for organic impurities shall show a colour not deeper than that of the standard solution. The amount of fine particles, as ascertained by the laboratory sedimentation method, shall not exceed 10% for crushed stone sand nor 4% for natural sand. The field sedimentation test shall yield a percentage clay-plus-fine-silt not exceeding 10% for natural sand. These tests are to be conducted in accordance with S.S.73.
(iii) If the fine aggregate does not conform to the prescribed standards, the S.O. may reject it or order that it be washed, screened and graded until it meets with his approval.
(iv) The grading of fine aggregate for concrete work shall comply with the requirements of S.S.31.
(v) The fine aggregate must be within the limits of grading zone 2 for Grade 30 and Grade 25 concrete and within the limits of grading zones 1 & 3 for Grade 20 and Grade 15 concrete. The grading zones are those specified in Table 2 of S.S.31. The use of all-in aggregate will not be permitted.
(vi) The Contractor is required to provide an approved type of instrument/equipment for measuring, the moisture content in the fine aggregate (sand) for the concrete. Check on the moisture content of sand should be made at least once a day before concreting. The amount of water to be added to the concrete mix should be adjusted accordingly.
(i) Coarse aggregate must be crushed or uncrushed gravel or crushed stone and must be free from decomposed stone, clay, earth or other deleterious substances. The pieces must be angular, or except for concrete surfaces subject to abrasion rounded in shape and shall have granular or crystalline or smooth (but not glassy) non-powdery surfaces. Friable, flaky and laminated pieces, mica and shale can only be present in such quantities as not to affect adversely the strength and durability of the concrete.
(ii) The maximum size of coarse aggregate for Grades 30, 25, 20, and 15 concrete shall be 20mm. The grading of coarse aggregate for concrete work shall comply with the requirements of S.S.31.
(a) Water for making concrete and cement mortar must be clean, fresh and free from organic or inorganic matter in solution or suspension in such amounts that may impair the strength or durability of the concrete. Water must be obtained from a public supply where possible and can be taken from any other source only after comprehensive testing and analysis of samples and the written approval of the S.O.. No sea-water or water from excavation can be used.
(b) Only water of approved quality can be used for washing out shuttering, curing concrete, testing water retaining structures and similar purposes.
(a)The reinforcement shall be complying with S.S.2, S.S.18 or steel fabric complying with S.S.32.
(b) Where the letter T is used in the structural detailing, it shall mean that such reinforcement shall be high-yield bars having a minimum characteristic strength of 460N/mm2 unless otherwise stated.
(c)The letter R, where used shall indicate that such reinforcement shall be mild steel bars with a minimum characteristic strength of 250N/mm2.
(d)Reinforcement bar not designated by any letter shall be high yield having a minimum characteristic strength of 460N/mm2.
(e)Neither the nominal size nor the letter of a bar shall be less than the size or length shown on the drawings.
Structural steel members shall comply with the requirements of B.S.4360 and be of uniform sizes and standard cross section.
42TESTING OF STEEL
(a)The Contractor shall arrange for the manufacturer to supply direct to the S.O. a certificate stating the process of manufacture and a test sheet signed by the manufacturer giving the results of each of the mechanical tests applicable to and the description of the materials purchased and, if and when the required, of the chemical analysis also and all tests specified in the relevant Standards.
(b)The reinforcement shall be tested based on the frequency as shown below. Selection of test pieces shall be made by the S.O.. The Contractor shall bear all costs involved in making these tests.
Type of Test
Frequency of Test
One sample for every 500Ton or rebars or part thereof
One sample for every 25Ton of rebars or part thereof
One sample for every 50 Ton of rebars or part thereof
Mild steel dowel bars shall consist of steel complying with the requirements of B.S.4360. They shall be straight 20mm diameter, 450mm long and free from burned edges or other irregularities. The bars are to be included in the works where indicated on the drawings or directed by the S.O.. In general, half the bar shall be connected in on one side of a break joint and the other half painted with bitumen before concreting in on the second side of the break joint.
Waterproof building paper shall comply with B.S.1521. For roadworks, it shall be Class "B".
45EXPANSION JOINTING MATERIAL
Expansion jointing material shall be supplied in the required thickness and widths. No multi-layer joints will be permitted. The material shall comprise an approved cellular material with a high degree of recovery after crushing and the material shall be thoroughly impregnated with a suitable preservative.
46JOINT SEALING COMPOUND
Joints shall be sealed with a rubber-bituminous compound which shall be of an approved type compatible in all respects with the jointing material. Horizontal joint seals may be made with a hot run type of sealer while vertical joints shall be made with a caulked, or adhesion type sealing strip. Full details of the materials and the manufacturers recommendations for application shall be submitted to the S.O. for approval.
(a) Water bars shall be of an approved type and shall be obtained from an approved manufacturer. They shall be of a natural or synthetic rubber, extruded P.V.C. plastic or copper strip. The copper strip shall comply with B.S. 1878, shall be of adequate gauge and shall not be perforated.
(b) The rubber or P.V.C. strips shall be of adequate dimensions generally not less than 150mm wide x 6mm thick with keys at each end and a central shear bulb.
48REQUIREMENTS ON PRECAST CONCRETE UNITS
The Contractor is required to submit to the S.O. for approval prior to the construction, his proposal for handling and lifting these precast units. His proposal shall include detailed drawings and calculations certified by a Professional Engineer to be engaged by him. The lifting arrangement shall be so designed so that no undue stresses will be induced on the precast units. If the lifting arrangements are so designed that additional reinforcements are required to be provided in the precast units shown in the Contract Drawings, the Contractor shall provide the additional reinforcements required to the approval of the S.O. and he will not be allowed to claim for the additional reinforcements provided. The Contractor shall take note of the above and shall allow in his rates to comply with the requirements.
The Contractor shall ensure that all faces of the precast units which adjoin during construction shall be of such form and finish that the interior surface of the precast units shall be such as will facilitate the assembly of the precast units. Unless otherwise stated, the joint between adjacent precast sections may be a rebated joint.
The Contractor shall ensure that the actual internal dimensions of a precast section shall not differ from the designated dimension by more than 5mm, the actual thickness by more than plus 5mm or minus 3mm and the actual length by more than 6mm.
(d)WORKMANSHIP AND FINISH
The Contractor shall ensure that the concrete shall be dense and hard and substantially free from chipped edges, laitance and surface roughness, the precast sections shall be free from fractures and cracks wider than 0.15mm and residual test cracks wider than 0.08mm, and from other defects arising from faulty material or faulty methods of manufacture. Dents not exceeding 3mm deep and bulges not exceeding 3mm high shall be permitted provided that they do not extend over the surface for a distance greater than twice the thickness of concrete where they occur.
The date of manufacture of the precast units shall be clearly stencilled on the interior of each unit near the top.
Except in cases where the design is done by the Board and the precasting is done under the supervision of the S.O. or where there are no Standards & Specifications available, from every twenty units of the precast sections of each type and size manufactured, the S.O. may select one unit for load test. The load test will be carried out as directed by the S.O. and in accordance with the requirements as spelt in the Contract Specifications.
The Contractor shall also note that he is required to find his own casting yard at his own cost. The Contractor shall then notify the S.O. of the location of his casting yard. The S.O. and his representatives shall have access to the casting yard at all reasonable hours. The Contractor shall make arrangement for the testing of the concrete cubes for the precast units in accordance with the procedure as stipulated in the Standard Specification for Drainage Works. The cost of making, curing, transporting and testing of all the cubes shall be borne by the Contractor.
Any unit which is found to be defective or damaged during handling shall be rejected. All rejected units must be removed from the site. The rejection of any precast unit shall be made for the precast units which are rejected
(i)LAYING OF UNITS
The Contractor shall ensure that the precast units are laid to the correct line and level. The Contractor shall be required to take out and adjust the precast units at his own cost if there is any movement or settlement of the units during and after construction. The Contractor is to allow in his rates for cement grouting or equivalent approved filling of the gaps between the adjacent precast units to the full satisfaction of the S.O..
(j)METHOD OF CONSTRUCTION
The Contractor shall be required to submit a detailed description of the method of construction of the precast units including the type of machinery to be used for the approval of the S.O. before the commencement of work.
The Contractor will be required to supply samples of all precast concrete units for the approval of the S.O.. Only when approval has been given may the supply of the units take place and any units supplied which are inferior to the approved sample will be rejected.
49PRESTRESSED CONCRETE SLAB
(a) The prestressed concrete slabs required as cover slabs to access chambers etc. shall be precast concrete units.
(b) The slabs shall be designed to carry a superimposed live load of 510kN/m2 where installation is outside the carriageways (medium) and Ministry of Transport (U.K.) loading for carriageway design (heavy). Calculations and design for each type of slab shall be submitted and approved by the S.O. before casting commences.
(c) Slabs shall be subjected to test before delivery to site, one slab being subjected to test for each batch or type of slabs of 25 or less made. The test units selected by the S.O. shall be subjected to a point load bending test, the load being sufficient to induce a bending moment not less than one and a half times the design moment. One slab of each size made shall be subjected to a test to failure to ascertain the ultimate bending moments.
50CONCRETE PIPE (ORDINARY PORTLAND CEMENT) WITHOUT LINING
(a)Concrete pipes shall be to the approval of the S.O. obtained from an approved manufacturer and made from reinforced Ordinary Portland Cement Concrete. They shall in general comply with S.S.183 and shall be tested as described therein. Drawings and details of the proposed reinforcement shall be submitted for the S.O.’s approval.
(b)In particular, the hydraulic proof test shall be to S.S.183 and shall be applied on 1 in every 50 or part of 50 pipes of the same nominal internal diameter for all sizes and classes of pipes.
(c)Standard pipes, Class L, M and H pipes shall be capable of being jointed one to the other in the normal manner.
(d) No pipes shall be dispatched from the place of manufacture until the approval of the S.O. has been given following whatever tests or inspection the S.O. may have called for. Notwithstanding the approval of the S.O. to pipes at the place of manufacture, the Contractor will still be held responsible for any faults found on the pipes on site.
(e)In order to permit the use of the same moulds for different classes of pipe specified, internal diameters greater than that specified will be permitted. The internal diameter of the finished pipes shall not be more than 25mm less than the diameter stated in the B.Q..
The sand for cement mortar etc. shall be as described for fine aggregate except that it shall be fine sand complying with S.S.31.
Granular material for pipe bedding etc., shall be of approved sand, laterite or other suitable material, free of all clay lumps and stones above a 25mm gauge.
Local stone rejects shall be not less than 75mm or more than 100mm gauge and shall be of a type approved by the S.O..
54STONE FOR PITCHING
Stone for pitching shall be of approved granite. No block shall exceed 0.03m3 in volume and its greatest dimension shall not exceed 450mm.
Hardcore shall consist of broken stone, brick, or other approved hard material. It shall be free from clay, dust and other deleterious matter and shall not contain pieces exceeding 150mm or less than 60mm gauge.
(a)Common bricks shall be of a standard size, of even shape, hard, well burnt, and machine made pressed bricks with true arrises.
(b)Facing bricks shall be of a standard size, uniform in dimension, shape and colour and shall be hard, well burnt, pressed bricks. The delivered bricks shall be further selected by hand picking on site to reject misshapen, underburnt or overburnt bricks. No payment will be made for rejected bricks although suitable rejects may be used as 'commons'.
(c)Engineering bricks shall be obtained from approved manufacturers. They shall be hand selected so that they will in general conform to S.S.103 but the minimum allowable average compressive strength shall not be less than 31 N/mm2. They shall be the best of their respective kinds, sound, hard, square made, well burnt throughout, regular in size and shape, with good faces and clean arrises and free from lime, chalk, pebbles, shell or other extraneous matter and other defects.
(d)Before any bricks are ordered, samples of each kind of brick shall be submitted to the S.O.'s representative for approval.
(e)Bricks shall be carefully handled from lorries and stacked by hand and all bricks broken, chipped, cracked or with broken arrises shall be removed from the site without delay.
57GRATING & CHEQUER PLATES FOR CLOSED DRAIN/CULVERT
(a)Standard gratings, chequer plates and frames shall comply with the Standard Drawings issued by the Drainage Department in all dimensional particulars.
(b)For gratings, chequer plates and frames not to standard dimensions and type, large scale sectional drawings must be submitted for approval before orders are placed.
(c)All gratings and chequer plates provided over closed drains/culverts shall be hinged to fixed frames securely embedded into the drain structures. The spacing of the hinged gratings shall be in accordance with the requirements of the relevant authorities. Mild steel heavy duty gratings shall be used for closed drains subjected to vehicular loadings, whereas light duty gratings shall only be used for pedestrian loadings. The gratings, frames and chequer plates shall be galvanised.
(a)Aluminium rungs shall be at 300mm centres and of 380mm width. The rungs shall be provided if depth of drains equal to or exceeding 1.2m and width of the drains equal to or less than 2m.
For closed drains, the rungs shall be provided at every 60m apart and for open drains, the rungs shall be provided at every maintenance openings/gratings according to the Code of Practice on Surface Water Drainage.
(b)The rungs shall be made of aluminium alloy 6082 T6 and of approved design complying with B.S.1474.
(a)Unless otherwise specified, handrailing and standards may be made from continuous weld hot dipped galvanised mild steel tube medium quality 30mm internal diameter, complying with S.S.17. Fittings for handrail standards shall comply with B.S. 1740.
(b)Alternatively, handrailing and standards shall be of extruded aluminium tube, 30mm outside diameter with robust cast aluminium standards to S.O.'s approval.
(c)The aluminium alloy shall be H30. The extruded aluminium members shall be fabricated from aluminium alloy HT30TF, HE30TF or HF30TF complying with B.S. 1471, B.S. 1472 or B.S. 1474 or equivalent.
(a)All paints including primers and undercoats shall be obtained ready mixed for use from approved manufacturers. The Contractor shall only be allowed to use paint which is delivered to the site in sealed cans or drums bearing the name of the manufacturer and properly labelled as to quality.
(b)All materials for multiple coats, e.g. priming, undercoat and finishing coat shall be obtained from the same manufacturer and shall be those recommended by the manufacturer as suitable for using together and for the surface concerned. All tints and shades (including undercoats) shall be selected and approved by the S.O..
(c) Priming paint for structural steel and cast iron shall comply with S.S.6: Types B or C. Priming paint for zinc or aluminium surfaces shall be approved zinc chromate priming paint. Oil-based undercoat and finishing paints shall be similar to S.S.34 and S.S.7 respectively, but the pigments shall not include white lead.
61EROSION CONTROL BLANKETS
(a)The work shall consist of furnishing, placing and maintaining the erosion control blanket (ECB).
(b)The blanket shall be a machine-produced mat of consistent thickness with coconut fibre or palm oil fibre, or other approved fibres with equivalent performance properties, stitched or otherwise mechanically bonded evenly over the entire area of the mat. The blanket shall be covered on both sides with photodegradable polypropylene netting and sewn together with polyester thread.
(c)The blanket shall have the following properties:
Weight of netting
Not less than 270 g/m2 + 10%
Mesh size of netting
Not more than 16mm x 16mm
Not less than 3 months
Palm oil fibres:
Weight of netting
Not less than 300 g/m2
Mesh size of netting
Not more than 19.2mm x 36.3mm top
Not more than 9.3mm x 8.5mm bottom
Not less than 3 months
Other materials subjected to approval:
Weight of netting
Not less than 270 g/m2
Mesh size of netting
Not more than 16mm x 16mm
Not less than 3 months
(d)The Contractor shall submit certified test data from the manufacturer covering each shipment of the material.
(e)Fasteners shall be used to anchor the blanket to the prepared ground/soil. The appropriate fasteners shall be used in accordance with the manufacturer's design and suitable for the ground conditions. Except grounds that will be protected for at least 12 months, metal or non-degradable fasteners are not permitted.
(f)The functional longevity of the blanket to be chosen depends on the dormant period of the bare ground. The longevity of the blanket shall be chosen such that erosion would be effectively under control at the bare ground covered with ECB throughout the dormant period of the bare ground. The Contractor shall ensure that no bare ground shall be left unprotected from erosion for a month or longer.
(g)The Contractor is deemed to have allowed in the contract for complying with the above requirements.
PART III - WORKMANSHIP
(a)The workmanship shall be of the quality specified. Where the quality of workmanship is not specified in this Specification or in the relevant S.S. or B.S. or elsewhere, work of first class workmanship shall be carried out. All persons employed on the Works or elsewhere in connection with the Works shall be competent and skilled in their respective occupations.
(b)The opinion of the S.O. regarding the standard of workmanship will be final and any work condemned as of inferior standard shall be cut out, removed and replaced to the full extent as directed by the S.O..
(a)The Contractor shall be deemed to have visited and examined the site carefully and to have ascertained the nature thereof and the kinds of materials to be excavated, and provision must be made in the prices to cover for the types of materials to be excavated.
SURVEY AND SETTING OUT BEFORE EXCAVATION WORK
(b)Prior to commencement of excavation, the Contractor shall set out the lines and structures for the inspection and the approval of the S.O.. Original ground levels shall also be taken and submitted to the S.O. for record.
(c)All excavations shall be carried out to the required lengths, breadths, depths, inclinations and curvatures as may be necessary for the construction of the Works or as shown in the drawings, in whatever material that may be found and his prices for excavation must include for any type of earth likely to be encountered i.e. soft earth, sand, soft clay, hard clay, tree roots etc., and the surplus soil shall be disposed off as specified hereinafter and as directed by the S.O..
(d)Excavations shall be performed in such a manner and by such methods as are required to maintain safe and stable slopes in the materials encountered, to support adjacent structures, roadways and pipes and to ensure the safety of workmen. No excavation, in areas requiring groundwater control unless sheeted and braced, shall be carried out with a slope steeper than 2 horizontal to 1 vertical.
(e)All excavations are to be carried out according to Part XII, Excavation Work of the Factories Regulations 1985 and all applicable safety regulations under the law of the Republic of Singapore.
(f)The Contractor shall only carry out trench excavation work provided the rate of construction keeps pace with the rate of excavation.
(g)Reuse of excavated material such as natural stone, artificial stone, brick, top soil etc.:
(i) When excavating carriageways, natural stone, artificial stone, brick or tar-paved footpaths or gravelled verges, the Contractor shall first remove all metals, slabs or bricks forming the existing paving to slightly more than the width of excavation and keep separate from the general excavated material for re-use in reinstatement. Breaking through road foundations and surfaces shall be allowed for in the rates for reinstatement together with the cost of temporary reinstatement to the satisfaction of the S.O..
(ii)Pipe trenches shall be cut to a sufficient width to receive and allow the pipes to be easily and properly jointed, but subject to the foregoing shall be kept to the minimum practicable width. The trench width may also be reduced at or about the pipe soffit level in order to reduce the formation level.
(iii)Any topsoil shall be excavated separately from the subsoil and shall be kept separate and be used to cover trenches, embankments, slopes, tips, verges, etc. The surfaces so covered shall be neatly trimmed to form smooth uniform slopes or level surfaces as when directed by the S.O..
(h)Stockpile of Excavation Material
(i)All surplus excavated materials shall be carted away to the Contractor’s own disposal ground immediately. The surplus excavated material shall not be stockpiled on site. No excavated material shall be allowed to be stockpiled adjacent to the excavations, and the Contractor shall, in general, carry out the whole of the excavation work in the following manner.
(ii)Upon the commencement of excavation work and at such other times as the S.O. may require, the Contractor shall cart the excavated material to a tip to be provided by the Contractor. When in the opinion of the S.O., sufficient excavated material has been carted to the aforesaid tip, the material subsequently excavated shall be carted to working sections on a completed portion of the work and used as backfilling on those sections when necessary on completion of the whole of the work, or at such other times as the S.O. may require, the excavated material previously taken to the tip provided by the Contractor, shall be carted back to the site for backfilling. If the tip provided by the Contractor is within the site, the tip area must be properly contained and covered to prevent earth from washing into the drains or canals.
(i)Measurement Of Excavation Work
(i) The quantities of excavation will be measured as the product of the net plan area of the structure and the vertical height of the agreed ground level above the formation levels of the structure or invert level in the case of a pipeline and the Contractor will be paid in accordance with the quantities thus ascertained. No payment will be allowed for any additional excavation which the Contractor may have to carry out for working space, timbering, shuttering, etc.
(ii)Where, in the opinion of the S.O., it is necessary for any reason to form, extend and/or deepen foundations under or around any parts of the Works and additional excavation so ordered by the S.O. will be paid for at the rates priced in the Bill of Quantities.
(a)Trial holes of such sizes and depths and in such position as may be necessary or directed by the S.O. shall be dug and immediately made good and surfaces reinstated to the original condition as may be ordered by and to the satisfaction of the S.O..
(b)Sufficient trial holes must be dug to accurately locate and determine the positions of services and obstructions in advance of the work. Trial holes may also be necessary to investigate or prove soil conditions in advance of the main excavation.
(c)In all cases, the trial holes are to be excavated, refilled and reinstated in accordance with the Specification for excavation, refilling and reinstatement.
(a)Where trial borings or tests have been made by the Department, the results may be made available to the Contractor. The results or any other information on strata is given in good faith but the Board accepts no responsibility for the accuracy or reliability of such information. In all cases, the Contractor will be deemed to have satisfied himself as to the type of strata and ground conditions to be encountered during the Works.
(b)Additional trials borings required by the Contractor to further investigate the soil conditions shall be carried out by the Contractor at his own expense.
66EXCAVATION IN ROCK
(a)Any rock met with in excavation to the required depths shall be removed by wedging, blasting or otherwise as the S. O. may direct. For the purposes of this Contract, rock shall be deemed to be hard natural material which cannot be excavated without the use of wedges, chisels, pneumatic drills or explosives. Unlaminated rock shall be hard sandstone or granite without bedding or cleavage planes. Laminated rock shall be hard shale or hard laterite in distinct layers and shall not include hard clay which shall be excavated at the normal rates for excavation
(b)The S.O.'s decision as to whether or not the material of the excavations is to be classified as rock shall be final and the Contractor will be paid extra over for excavation in rock as defined above at the rates quoted in the Bill of Quantities.
(c)The quantities of rock billed are PROVISIONAL but the Contractor's price for rock excavation will apply to whatever quantities are finally measured, at whatever depth the rock is encountered, and no claim will be considered which is based on a variation of quantities.
(d)In excavation for structures, the volume of rock paid for shall be the product of the actual area of rock, within the limits of the net plan area of the foundations, and the average thickness of rock excavated.
(e)In trenches, the volume of rock paid for shall be the product of the width of the relevant Type Section and the average thickness of rock excavated between the points concerned and the length thereof and as defined below.
(f)The volume of rock on which payment is claimed shall be measured and agreed upon weekly. No extra for rock shall be payable in any excavation in which the rock has been hidden or covered up prior to the volume of rock excavated being measured and agreed upon by the S.O.'s representative and the Contractor or in respect of any volume which has not been agreed upon within one week of the time the excavation was made.
(a)Blasting shall not be allowed without written permission from the S.O.. If explosives are to be used, the Contractor shall obtain all necessary licenses from the appropriate authorities and shall conform to all Government regulations relating to transport, storage, handling and use of explosives and shall also conform to the rules set out by the Officer-in-charge of Arms and Explosives.
(b)S.O. must be fully informed by the Contractor as to the steps and precautionary measures taken to safeguard the surrounding properties. The Contractor shall be liable for any accident, damage or injury to any person or property resulting from the use of explosives. When blasting is proposed to be carried out, the Contractor shall determine the danger zone likely to be created and ensure that no damage is caused to person or property on or off site. Prior to commencing blasting operations, a written report supported by photographs listing any existing defects in structure shall be submitted to the S.O..
(c)When blasting operations are being carried out, any road affected shall be closed to traffic and appropriate signs shall be erected in accordance with the latest ‘Code of Practice’ by LTA.
(a)Where excavation has been carried out on plan in excess of the limits of permanent work for which it is intended, the S.O., may require the Contractor to fill the void so formed with compacted materials of a similar nature to the adjacent work. Where excavation has been carried out to a depth greater than that required, the void so formed shall be filled with mass concrete as directed by S.O.. In both cases this filling shall be done at the expense of the Contractor.
(b)After excavating the sites on which the various parts of the works are to be constructed, if it is found that due to no fault of the Contractor any part of the formation is unsuitable to provide a satisfactory foundation, such portions shall be further excavated to such depths as the S.O. may direct and refilled to original formation level with mass concrete or hardcore or quarry waste as may be directed. Payment will be made for such additional excavation and filling at appropriate rates.
68PREVENTING DAMAGE DUE SUBSIDENCE
When any excavation is carried out near, or under any existing work including buildings, services, mains, cables, and surfaces such as roads, etc. liable to be affected by subsidence, the Contractor shall prevent damage by subsidence, whether such existing work is shown on the drawings or not.
69TIMBERING OF EXCAVATION
(a)The term "timbering" shall cover all necessary methods of support including the use of timber, concrete, steel sheet piling, steel sheeting or such materials as may be approved by the S.O. If timber is used, it shall be of the species Keruing or Kempas.
(b)The Contractor shall supply and fix strong and sufficient timbering to support the sides and/or bottom of the excavation to the satisfaction of the S.O. and shall maintain the same until the constructional work is sufficiently advanced, in the opinion of the S.O. to permit the timbering to be withdrawn, which shall be conducted only under the personal supervision of a competent person employed by the Contractor.
The Contractor shall carry out such timbering and shoring with due consideration to full flow or flooding conditions all to the satisfaction of the S.O..
(d)The Contractor is required to submit to the S.O. drawings and calculations showing details of the proposed timbering for approval. Where excavation exceeds a depth of 4m, the Contractor is required to engage a registered Professional Engineer to submit the design and supervises the erection of the timbering. No excavation work may start until the timbering details are approved. Where excavations for culvert structures are required, the Contractor must submit the full details of the proposed timbering methods within one month of the date of Acceptance of Tender. Failure to submit and obtain approval of details expeditiously may result in delays with a consequent claim for damage. The Contractor shall not be entitled to any extension of Time for Completion on this ground. Notwithstanding the approval given, the S.O. reserves the right to instruct the Contractor to improve, alter, revise and strengthen the timbering from time to time.
(e)The Contractor shall be responsible for any injury to the work and any consequential damages caused arising out of the removal of the timbering and any advice, permission or approval given by the S.O. relating to the removal of timbering shall not relieve the Contractor from the responsibility specified in the Contract.
f)The S.O. shall have the right to order excavation and construction work to be carried out in such lengths and in such sections of the Works, as will, in his opinion, minimise the danger of such open excavation affecting the stability of any nearby structures or ground, and the Contractor shall have no claim for extra payment on this account. Shoring timbers shall be removed as the work proceeds only if their removal does not endanger existing adjacent structures. Where the S.O. deems it dangerous to remove the shoring timbers, such timbers shall not be removed.
The Contractor shall be paid for all timbering left in the excavations on the instruction of the S.O. provided the timber is required to give permanent support to trench sides, services or building. No payment shall be made where timber has to be left in, on the instruction of the S.O. to counter any defect or negligence in the Contractor's execution of the work. Only the actual quantity of timber left in shall be paid. Payment shall not be made for labour in cutting nor for timber in ends thus cut off, nor for the disposal of additional surplus excavated materials due to the leaving in of timber.
71STEEL TRENCH SHEETING
(a)Where the subsoil conditions are expected to be of a soft and unstable character in trench excavation, the normal methods of timbering will probably prove inadequate to avoid subsidence of the adjoining road surfaces and other services. The Contractor shall be responsible for all such damages as specified elsewhere.
(b)In such circumstances the Contractor shall use Steel Trench Sheeting or Sheet Steel piling adequately supported by timber struts, walings, etc. The Contractor shall be expected to supply, pitch, drive and subsequently remove trench sheeting or piling in accordance with other timbering items specified in the Specifications and the terms Timber or Timbering shall also apply to Steel Trench Sheeting or Sheet Steel Piling throughout.
72STEEL SHEET PILING
(a)The Contractor shall be at liberty to use steel sheet piling for any purpose during the construction of the works, subject to the approval of the S.O. and shall bear all and every expense in connection therewith, including waste and burning off piles if necessary.
(b)Steel sheet piles shall conform to the provisions of B.S.4360 and shall be driven where required and approved or directed by the S.O..
(c)The Contractor is required to engage a registered Professional Engineer to design the layout of the piling and the overall dimensions of the excavation to suit the sheets and corners available and to give sufficient working space for the proper construction of the work. For purposes of this Contract, it shall be clearly and definitely understood that the terms 'timber' or 'timbering' as used in any portion of the Specifications, shall be deemed to include 'Steel Sheet piling'.
73LIABILITY FOR TIMBERING
(a)No work done by the S.O. or the fact that the timbering has complied with the Specification shall absolve the Contractor from his responsibility. The Contractor shall be responsible for making good any damage caused as a result of the timbering failing to give proper support to the sides of the excavation.
(b)The timbering to the sides of excavation for structures shall be carried out in such a way that there is no obstruction caused to the fixing of formwork for the walls. The supporting strut and walings shall be removed by the Contractor in stages to suit the progress of concreting.
(c)If the S.O. is not satisfied that the standard of timbering is equal to that shown on the approved drawings or that the sides of the excavations have not been secured in a manner to render such excavations safe for working, he may, after giving the Contractor or his representative one hour notification in writing, instruct another party to supply labour, material, plant, implements and transport to alter the timbering and the cost of such works shall be paid for by the Contractor.
(a)The Contractor shall note that no existing watercourse shall be filled up until proper diversion drains are provided. The Contractor shall ensure that there is no blockage in the existing drains and storm water can be effectively drained.
(b)Excavated surfaces upon or against which concrete is to be deposited shall be kept dry and clean. Special precautions are to be taken to prevent water from washing out cement or fines whilst the concrete is setting.
(c)The Contractor shall keep all excavations clear of water. He shall also take care that at all stages of the Work, the sites are kept properly drained and that standing pools of surface water are not allowed to form.
(d)The Contractor shall drain and dry out the cut area and keep the excavation free from water and mud from any sources. He shall provide and maintain an approved system of temporary drains, cut-off drains, sumps, pumps, well-points, dewatering equipment and all other measures to keep surface water out of the excavation and to remove from the excavations, surface water, sub-soil water or water from any other source. The Contractor shall supply all pumps, fuel, labour, attendance etc., to deal with any dewatering within the excavation and the working site as directed by the S.O..
(e)The Contractor shall construct and maintain such temporary drains as may be necessary to remove water from the excavation to existing drains and to drain any ponds which may have formed in the site. Water from the work shall be conveyed in such a manner as not to cause any nuisance or injury to the public.
(f)The Contractor shall execute the above with due consideration for full flow conditions and the execution shall be such that damages to construction works and flooding to the surrounding catchment shall be the minimum possible under the worst flood conditions.
(g)The Contractor shall be responsible for preventing silt or debris of any kind from entering the drains. Any silting of the watercourses and drains arising from the Contractor’s failure to comply with this clause shall be removed at his own expense whether or not within the site.
(h)On completion of the work, all temporary drains, ditches, sumps, etc. shall be demolished and the ground shall be reinstated to its original condition and to the S.O.’s satisfaction.
The Contractor shall provide adequate ventilation and efficient apparatus to keep all excavations, trenches and structures, pipelines and manholes free from gases whether generated in the strata, arising from the use of explosives for blasting, sewerage gases or otherwise and he shall take precautions to ascertain that they are in a safe condition before allowing workmen to proceed.
(b)WHEN WORKING IN CULVERTS AND CLOSED DRAINS
(i) A combustible gas detector and an oxygen meter should be used to test for combustible gases and oxygen at the entrance to a culvert or at the opening of manhole before forced ventilation of the culvert or manhole is carried out.
(ii) The manhole, culvert or closed drain must be adequately forced ventilated before workers go in for work. Ventilation must be continued without stoppages while the workers are inside.
(iii) The workmen should thoroughly check the whole closed drain or culvert (within which they are working) for combustible gas and oxygen.
(iv)Lifelines should be attached to workers going into culverts and closed drains.
(v)Workers should quickly come out of the culvert or closed drain when combustible gas or oxygen deficiency is detected. When combustible gas is detected, no naked flames and smoking should be allowed near the affected area. The PowerGas Pte Ltd must be immediately notified.
76APPROVAL OF EXCAVATION
The Contractor shall report to the S.O. wh